The present invention relates generally to supersonic combustion ramjets (i.e., scramjets), and more particularly, to a scramjet engine having improved mixing of fuel and air.
A scramjet engine typically powers an aircraft at relatively high supersonic, or hypersonic, velocities in freestream, or ambient air. The scramjet engine is conventionally designed for receiving supersonic freestream airflow and channeling such airflow at supersonic velocity through the scramjet engine. The supersonic ambient airflow is typically compressed internally in the scramjet engine in an inlet thereof which is typically a supersonic diffusor. The ambient airflow may be initially externally compressed by shockwaves generated off the aircraft's bow by recompression before entering the inlet.
The supersonic compressed airflow is channeled through the inlet and into a combustor where it is mixed with fuel, such as hydrogen, for combustion. Combustion gases generated in the combustor are discharged through a conventional exhaust nozzle for powering the aircraft at hypersonic velocities up to about Mach 18, for example.
Mixing of the fuel, such as for example hydrogen, and air in the scramjet combustor is a difficult process since the compressed airflow is flowing at supersonic velocity with substantial momentum, and the fuel injected into the combustor has relatively low momentum. Oxygen and nitrogen molecules contained in the airflow have relatively large mass inertia which typically easily overcome the relatively low mass inertia of molecular hydrogen in the fuel. Accordingly, hydrogen fuel has the tendency to simply follow the stream of supersonic airflow without significant mixing. In order for obtaining acceptable combustion in the scramjet combustor, acceptable mixing of the fuel and supersonic airflow must be obtained.
It is not believed that a scramjet-powered aircraft has yet been built or flown. However, small research-type scramjet engines have been built and laboratory tested at simulated flight speeds up to about Mach 7. Accordingly, the references herein to conventional and typical scramjets and structures refers to information conventionally known to those skilled in the art of engines for powering aircraft at supersonic velocity, which is based, in part, on mathematical modeling and analysis.